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In Elements of Chemistry by Antoine Lavoisier, he details a pair of experiments used to determine atmospheric composition:

First, he allowed mercury to simmer in a fixed volume of air over several days, leading to the formation of a red powder (mercuric oxide).

The leftover gas was seen to extinguish flames and suffocate animals.

Lavoisier was then able to heat the mercuric oxide to recover the oxygen, which was proven to feed flames and be respirable by animals.

I'd LOVE to show this sequence of experiments to my high school class, but the use of mercury is prohibited in the classroom.

I'm looking for a replacement for these two experiments. Iron oxide would be easy to form, but the heat required to thermally decompose it is likely excessive, especially if I'm hoping to recapture the released oxygen.

Any suggestions of metal oxides that can be easily formed and decomposed to recreate Lavoisier's experiment?

Or perhaps a different series of experiments that accomplish the same goal?

Many thanks.

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You can replace $\ce{HgO}$ by $\ce{Ag2O}$ which is also decomposed by heat (Bunsen burner) into metal + oxygen. The only trouble is that this silver oxide can be decomposed by heat, but it cannot be formed like $\ce{HgO}$ by heating the metal in air. $\ce{Ag2O}$ is formed in an aqueous solution of silver nitrate $\ce{AgNO3}$ after adding a $\ce{NaOH}$ solution in stoichiometric amounts, and filtrating the $\ce{Ag2O}$ precipitate.

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You might try electrolysis, rather than heating.

For example $\ce{2H2O->2H2 + O2}$.

  • Show that the oxygen derived support combustion. It could keep an insect or spider alive for hours, though I don't recommend animal experiments.
  • Show that the hydrogen derived ignites.
  • Show that the output from both sides can be combined to make an oxhydrogen torch (purge the apparatus before trying this, and use an explosion shield), and capture the water given off by the torch. For moderate currents, this should not produce excessive heat, though the temperature of even a tiny stoichiometric mix flame can reach 2,800 °C. However, for safety, rather than combining $\ce{H2 and O2}$ outputs as shown in that video, it might be safer to use an annular needle design, combining them only at the exit.

BTW, one might consider $\ce{H2O}$ a metallic oxide. Hydrogen is in Group I and behaves as a metal, if really pressed. ;-)

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